Closing Down Sale: Everything Must Go

It was the selling of dead people's stuff that lead to the extinction of the human race. Humans loved a bargain and with costs and overheads low, there was a tidy profit to be made on sales 'from the other side'. The high street chains couldn't compete with these low prices, neither could the online retailers, as dead people's stuff was ordered by ouija board (a precursor to the internet).

Governments hated this 'Zombie Economy' because the deceased didn't pay tax. Only the dead prospered, so...traders began declaring themselves dead, for tax purposes. All legitimate and completely legal, joining the growing hordes of the 'paperwork deceased' was an upward trend. Whole companies died and sales flourished. Business had never been better. Until everyone died.

Suddenly there no longer was an advantage in being dead and the Zombie Economy crashed. There was a vague attempt to jump-start business by the resurrectionists, but death is basically a one-way street.

Sadly Earth was subject to a hostile take-over by an interstellar group of corporate aliens who bought the planet for a song (and a bad one at that). They ground our globe to dust and sold it as organic compost. Humans had no legal means to protest, on paper everyone was technically dead. They'd inadvertently sold their souls. So, the human race was in big trouble. With no further options left, extinction was the only way to go. Just hope the insurance pays out.